This invention relates to battery power management technology, and more particularly, to a rechargeable-battery protection circuit with an alarm unit for use on an electronic system with a rechargeable battery unit, such as a notebook computer with a lithium-type rechargeable battery unit, the circuit protecting the rechargeable battery unit against over voltage/current.
There are two types of batteries: rechargeable and non-rechargeable. The non-rechargeable type is intended for one-time use and is discarded after the battery power is exhausted; whereas the rechargeable type can be repeatedly recharged after the battery power is exhausted. Portable electronic systems, such as notebook computers, are typically equipped with rechargeable batteries, such as the well-known lithium batteries, so that they can be repeatedly recharged for use while traveling.
The lithium-type rechargeable batteries have the benefits of having a larger capacity, being light weight, having an extended life, providing high output power, and having a fast recharge cycle. One drawback to the use of lithium-type rechargeable batteries, however, is that they are easily damaged by an over voltage/current condition; i.e., when a lithium-type rechargeable battery is subjected to an overly high recharging voltage exceeding 4.5 V (volt) or an overly low voltage below 2.2 V. Such over voltage/current conditions may cause permanent damage to the lithium-type rechargeable battery. Therefore, to protect the from this type of damage, a protection circuit is coupled to the lithium-type rechargeable battery.
FIG. 1 is a schematic block diagram showing the architecture of a conventional rechargeable-battery protection circuit. As shown, this rechargeable-battery protection circuit is designed for use with a rechargeable battery unit 100, such as a lithium-type rechargeable battery unit, for protecting the rechargeable battery unit 100 against over voltage/current during the recharging process. The architecture of this rechargeable-battery protection circuit includes an over voltage/current detection circuit 110, a microprocessor 120, and a recharging circuit 130.
The over voltage/current detection circuit 110 has a voltage/current input port A1 and a signal output port A2. The voltage/current input port A1 is coupled to receive the output voltage/current V/I of the rechargeable battery unit 100. The internal circuitry of the over voltage/current detection circuit 110 checks whether the output voltage/current V/I is over voltage/current or not. If YES, the over voltage/current detection circuit 110 will output an abnormal signal SI from its signal output port A2 to the microprocessor 120.
The microprocessor 120 has a signal input port B1 and a signal output port B2. The signal input port B1 is coupled to receive the abnormal signal S1 from the signal output port A2 of the over voltage/current detection circuit 110, and the signal output port B2 is used to output a recharge-disable signal S2 to the recharging circuit 130.
The recharging circuit 130 has a signal input port C1 and a voltage output port C2. The signal input port C1 is coupled to receive the recharge-disable signal S2 from the signal output port B2 of the microprocessor 120. The voltage output port C2 is coupled to the rechargeable battery unit 100 so that the recharging circuit 130 may recharge the rechargeable battery unit 100.
In the event of the rechargeable battery unit 100 having an over voltage/current condition, it will be promptly detected by the over voltage/current detection circuit 110. In response, the over voltage/current detection circuit 110 outputs an abnormal signal S1 to the microprocessor 120. The microprocessor 120 takes the abnormal signal S1 as an interrupt and promptly outputs a recharge-disable signal S2 to the recharging circuit 130. Upon receiving the recharge-disable signal S2, the recharging circuit 130 immediately stops the recharging process and uses DC-to-DC conversion technology to lower the charging voltage/current on the rechargeable battery unit 100 in order to protect the rechargeable battery unit 100 against over voltage/current damage.
One drawback to the rechargeable-battery protection circuit of FIG. 1, however, is that when the over voltage/current condition occurs the protection circuit may not always be able to stop the recharging process for one or more reasons including:
(1) the microprocessor 120 fails to receive the abnormal signal S1;
(2) the microprocessor 120 fails to output the recharge-disable signal S2 in response to the abnormal signal S1; or
(3) the recharge-disable signal S2 fails to disable the recharging circuit 130 to stop the recharging process on the rechargeable battery unit 100.
Should any one of the above conditions happens, the recharging process will continue and eventually cause over voltage/current damage to the rechargeable battery unit 100. There exists, therefore, a need for a solution to this problem.
It is therefore an objective of this invention to provide a rechargeable-battery protection circuit with an alarm unit which can generate a human-perceivable alarm to alert the user to the over voltage/current condition. The user may then take the necessary actions to protect the rechargeable battery unit against over voltage/current damage.
In accordance with the foregoing and other objectives, the invention proposes a novel rechargeable-battery protection circuit with an alarm unit for use on an electronic system with a rechargeable battery unit. Such a circuit will help protect the rechargeable battery unit against over voltage/current damage.
The rechargeable-battery protection circuit of the invention comprises: (a) an over voltage/current detection circuit coupled to the rechargeable battery unit for detecting an over voltage/current condition from the rechargeable batteryxe2x80x94if such a condition is detected, the detection circuit generates an abnormal signal and an alarm-enable signal; (b) a microprocessor, which is capable of generating a recharge-disable signal in response to the abnormal signal from the over voltage/current detection circuit; (c) a recharging circuit for performing a recharging process on the rechargeable battery unit, the recharging circuit being capable of stopping the recharging process in response to the recharge-disable signal generated by the microprocessor; and (d) an alarm unit, which is capable of generating a human-perceivable alarm in response to the alarm-enable signal generated by the over voltage/current detection circuit.
The rechargeable-battery protection circuit of the invention is characterized by the provision of the alarm unit, which is used to generate a human-perceivable alarm to alert the user to the over voltage/current condition. The user may then take the necessary manual actions to protect the rechargeable battery unit against over voltage/current damage. This allows the rechargeable battery unit to be more reliably protected than the prior art.